\ncongThe symbol \ncong is used to denote that two mathematical expressions are not congruent. In geometry and algebra, congruence refers to the equivalence of shapes or numbers under certain operations or transformations. The negated symbol \ncong indicates that such equivalence does not hold between the given expressions.
The triangles ABC and DEF are not congruent.
\triangle ABC \ncong \triangle DEFThe numbers a and b are not congruent modulo n.
a \ncong b \pmod{n}The functions f(x) and g(x) are not congruent.
f(x) \ncong g(x)